Active Directory Read-Only Domain Controller (RODC)

What are RODCs? What are advantages?

A read-only domain controller (RODC) is a new type of domain controller in the Windows Server® 2008 operating system. With an RODC, organizations can easily deploy a domain controller in locations where physical security cannot be guaranteed. An RODC hosts read-only partitions of the Active Directory Domain Services (AD DS) database.

Before the release of Windows Server 2008, if users had to authenticate with a domain controller over a wide area network (WAN), there was no real alternative. In many cases, this was not an efficient solution. Branch offices often cannot provide the adequate physical security that is required for a writable domain controller. Furthermore, branch offices often have poor network bandwidth when they are connected to a hub site. This can increase the amount of time that is required to log on. It can also hamper access to network resources.

Beginning with Windows Server 2008, an organization can deploy an RODC to address these problems. As a result, users in this situation can receive the following benefits:

§  Improved security

§  Faster logon times

§  More efficient access to resources on the network

What does an RODC do?

Inadequate physical security is the most common reason to consider deploying an RODC. An RODC provides a way to deploy a domain controller more securely in locations that require fast and reliable authentication services but cannot ensure physical security for a writable domain controller.

However, your organization may also choose to deploy an RODC for special administrative requirements. For example, a line-of-business (LOB) application may run successfully only if it is installed on a domain controller. Or, the domain controller might be the only server in the branch office, and it may have to host server applications.

In such cases, the LOB application owner must often log on to the domain controller interactively or use Terminal Services to configure and manage the application. This situation creates a security risk that may be unacceptable on a writable domain controller.

An RODC provides a more secure mechanism for deploying a domain controller in this scenario. You can grant a non administrative domain user the right to log on to an RODC while minimizing the security risk to the Active Directory forest.

You might also deploy an RODC in other scenarios where local storage of all domain user passwords is a primary threat, for example, in an extranet or application-facing role.

How do you install an RODC?

1 Make sure you are a member of Domain Admin group

2. Ensure that the forest functional level is Windows Server 2003 or higher

3. Run adprep /rodcprep

3. Install a writable domain controller that runs Windows Server 2008 – An RODC must replicate domain updates from a writable domain controller that runs Windows Server 2008. Before you install an RODC, be sure to install a writable domain controller that runs Windows Server 2008 in the same domain. The domain controller can run either a full installation or a Server Core installation of Windows Server 2008. In Windows Server 2008, the writable domain controller does not have to hold the primary domain controller (PDC) emulator operations master role.

4. You can install an RODC on either a full installation of Windows Server 2008 or on a Server Core installation of Windows Server 2008. Follow the below steps:

§  Click Start, type dcpromo, and then press ENTER to start the Active Directory Domain Services Installation Wizard.

§  On the Choose a Deployment Configuration page, click Existing forest, click Add a domain controller to an existing domain

§  On the Network Credentials page, type the name of a domain in the forest where you plan to install the RODC. If necessary, also type a user name and password for a member of the Domain Admins group, and then clickNext.

§  Select the domain for the RODC, and then click Next.

§  Click the Active Directory site for the RODC and click next

§  Select the Read-only domain controller check box, as shown in the following illustration. By default, the DNS server check box is also selected. To run the DNS server on the RODC, another domain controller running Windows Server 2008 must be running in the domain and hosting the DNS domain zone. An Active Directory–integrated zone on an RODC is always a read-only copy of the zone file. Updates are sent to a DNS server in a hub site instead of being made locally on the RODC.

§  To use the default folders that are specified for the Active Directory database, the log files, and SYSVOL, clickNext.

§  Type and then confirm a Directory Services Restore Mode password, and then click Next.

§  Confirm the information that appears on the Summary page, and then click Next to start the AD DS installation. You can select the Reboot on completion check box to make the rest of the installation complete automatically